The present invention relates to an improvement of a thermal ink transfer printing system, for the use of, for instance, facsimile and/or a printer, and, in particular, relates to such a system which may print color picture.
A thermal ink transfer printing system has the advantages, among others, that it has less mechanical moving members, the printing noise is low, the size of an apparatus is small, and it operates with low power voltage. Therefore, such printer has been utilized in a various kind of recording and/or printing systems.
FIG. 1 shows the principle of a conventional ink transfer printer. The numeral 1 is an ink film or a ink ribbon, 2 is a recording paper, 3 is a thermal printing head, 4 is a heater mounted in the thermal printing head 3, and 5 is a platen roller. The ink film 1 includes the lamination of the support film 1a of, for instance, polyethylene tere-phthalate film, and ink layer 1b painted on support film 1a. The ink film 1 and paper 2 are pressed on thermal printing head 3 by platen roller 5. When heater 4 of thermal printing head 3 is heated according to the picture pattern to be printed, ink layer 1b at thermal printing head 3 is selectively melted and transferred to the paper 2. Thus, the ink pattern is printed on paper 2. In operation, both paper 2 and ink film 1 move so that a fresh ink layer is always provided for fresh printing.
FIG. 2 shows a cross section of a conventional thermal printing head 3, and the numeral 3.sub.1 is a ceramic substrate, 3.sub.2 is a glaze layer, 3.sub.3 is a resistor (heater) layer, 3.sub.4 is an electrode, 3.sub.5 is a protection layer for preventing wearing and oxidization of a resistor layer 3.sub.3. The structure of the thermal printing head of FIG. 2 is the same as that which is used for a conventional thermal printer which uses a thermosensitive paper.
However, a conventional ink transfer printing system has the disadvantages that a moving means for moving an ink film 1 must be provided, and that an ink film can't be used twice. Therefore, a conventional printer must have means for winding up a used ink film, or at least a used ink film must be taken out of the printer apparatus. Although a recording paper 2 is relatively inexpensive, an ink film 1 is expensive. Therefore, the total running cost of the printer is high, and further, it is troublesome to mount and take off an ink film 1. Further, an ink film 1 is wrinkled because of thin film (which is 5-20 .mu.m in thickness), and in that case, the printing quality is considerably decreased.
It should be noted that the disadvantages of the conventional ink transfer printer mentioned above come from the structure through which the ink film must move. The Japanese patent laid open publication No. 178784/82 has proposed a printer which does not move an ink film. FIG. 3 shows the structure of the printer of that Japanese patent laid open publication.
In FIG. 3, the ink roller 6 rotates, and the pre-heater 7 is located close to the ink roller 6, and the thermal printing head 3 confronts with the ink roller 6. A recording paper 2 is located between the ink roller 6 and the thermal printing head 3, and the thermal printing head 3 presses the ink roller 6 through the paper 2. The numerals 8 and 9 in FIG. 3 are guides for moving the paper 2, and 10 is a protection cover. The ink roller 6 is made of sintered metal, which has fine pin holes including thermosensitive ink with dye, paint, wax, and/or some additives. The ink roller 6 is pre-heated by the pre-heater 7 so that the ink included in the roller 6 does not attach on the paper 2. The thermal printing head 3 heats the roller 6 selectively so that the ink is melted, and the melted ink is transferred to the paper 2. The ink roller 6 can be used for a long time, since the ink comes to the surface of the same from the inner holes.
The printer in FIG. 3 has the disadvantages that the head capacity of a thermal printing head must be large due to the heat loss of the thermal printing head which heats the ink roller through a paper with 50-80 .mu.m of thickness, and the printing resolution is small due to the thermal diffusion through the paper.